On return home from the NC Un Rally I started to notice the display voltage change from 13.1-13.5 VDC depending on throttle position, no throttle 13.5, hard pull 13.1, average 13.4 @ 350 hp.
Have noticed the different readings, just never put 2&2 together for 23 :headwall:
My question, what in the Cummins ECM / Allison 4000R would draw / lower the voltage depending on hp need. Am more familiar with the mechanical setups, the computers are more like black magic. Ideas ?
Dave, in many coaches of our age the ECM shares the same circuit as the condenser fan for the AC. That might be your culprit and a place to look
Hi John,
It is 100% throttle dependant, interesting, think need to yak with "the Brain @ FOT", see his opinion.
Might need a heavier wire from batteries to dash, or to ECM.
That is very interesting as I have noticed that when I am using throttle like going up a hill the battery voltage would go from 13.6 to 13.5, but I figured as long as it did not go lower than that I would not worry about it, I will be watching this to see what the answer is
I notice the same as Dave. If my start batteries are on float then after starting they are around 13.4 volts. At speed voltage slowly drifts down to 13.1 volts. With lights on and AC on it will go to 13 sometimes 12.9 volts. Slow down, come to a stop, back up to 13.4 volts. Start the generator to run roof top AC and start batteries go to 13.6 and stay there while gen is running.
I am thinking output voltage (under load) on the alternator needs to be upped a bit or maybe a smarter voltage regulator (like the one Sterling makes) might be the answer.
To my way of thinking after driving for several hours when I stop both sets of batteries should be at peak capacity. Or at least that is what I would like.
Roger